348 Sir W. Snow Harris on a General Law of 



times as great as tbe large jar B, and although the discharge 

 can pass over four times the distance as measured by a Lane's 

 electrometer. This experiment alone, without other considera- 

 tions, appears to me conclusive of the fact, that the hypothesis 

 of a variable " density " in the accumulated electricity has no 

 substantial foundation, at least so far as it relates to the intensity 

 indications of the electrometer. 



12. It is certainly true, as laid down by M. De la Rive in the 

 second volume of his recent work*, and as I long since deter- 

 mined f^ that the statical force of a given accumulation will, 

 under all circumstances, be in some inverse proportion to the 

 extent of the coated surface upon which the electricity is accu- 

 mulated ; and this is the case whether the increased surface be 

 derived from several jars, or from single jars of different magni- 

 tudes, although the precise reciprocal proportion of the surface 

 for the latter case may not probably coincide with that of the 

 first. This is, however, a very different affair to that of the effect 

 of the discharge of the accumulated electricity ; and M. De la Rive 

 is certainly inexact when, upon the authority of M. Riess, he 

 confounds the operation of the electrometer with " density," and 

 infers that this " density " is in proportion to the number of 

 equal jars of which the battery consists |. We should really be 

 led into serious errors in our analytical expressions if we assumed 

 the existence of any hypothetical quality such as " density," as 

 referable to the electrometer, the indications of which vary with 

 the extent of the battery upon far different principles. 



13. The whole of this question of "density" or "tension," 

 and " intensity," as it is sometimes denominated, referable to a 

 statical electrometer attached to the battery, is quite explicable 

 upon the principles of electrical induction. The active force of 

 any giv'en quantity of electricity accumulated on an insulated 

 conductor will be always apparently diminished by the influence 

 of a second neutral conductor in a perfectly free state, that is, 

 placed in communication with the ground, or otherwise by the 

 influence of a second insulated conductor charged with an oppo- 

 site electricity. This is really the great secret of the Leyden 

 experiment. In this case the action of the electricity accumu- 

 lated upon the inner coating is, as it were, masked, or rendered 

 more or less latent by the inductive action of the exterior coating 

 in communication with the earth, or by the influence of the op- 

 posite electricity. The force, therefore, in the direction of the 

 electrometer becomes neutralized to a greater or less extent by 

 the influence of the two coatings on each other acting in the 

 direction of the intermediate glass : the indicated intensity will 



* Vol. ii. p. 159. t Phil. Trans, for 1834. 



X Traife de I' Electricite, vol. ii. p. 159. 



